Field of the Invention
Embodiments of the present application relate to the art of a vehicle control system configured to operate a vehicle autonomously.
Discussion of the Related Art
JP-A-2014-106854 describes an automatic driving vehicle control apparatus includes: detection means for acquiring at least any of vehicle traveling state, vehicle surrounding state, and driver state; automatic driving means for automatically driving a vehicle; and determination means for determining whether a condition for automatic driving is satisfied or not. According to the teachings of JP-A-2014-106854, the determination means determines that the automatic driving condition is not satisfied when detection accuracy of the detection means does not satisfy a predetermined criterion. When the determination means determines that the automatic driving condition is satisfied, the vehicle is started the automatic driving. By contrast, when the determination means determines that the automatic driving condition is not satisfied during automatic driving, a warning is given to a driver to cancel the automatic driving. The automatic driving vehicle control apparatus taught by JP-A-2014-106854 is further configured to periodically calculate a stop spot where the vehicle can be safely stopped based on the vehicle surrounding state and the vehicle traveling stat, and to guide the vehicle to the stop spot when the driver does not cancel the automatic driving against the warning to cancel the automatic driving.
The vehicle to which the control apparatus taught by JP-A-2014-106854 is applied may be operated not only manually by a driver but also autonomously, with or without the driver or a passenger.
In a vehicle having a gasoline engine or a diesel engine, noises and vibrations are caused inevitably during operation of the engine and this may reduce ride comfort in comparison with the electric mode. According to the prior art, therefore, a limit value of an engine torque or power is set to reduce the noises and vibrations of the engine. For example, an operating region of the engine is restricted in such a manner that an engine speed is restricted lower than the limit value but an engine torque is restricted higher than the limit value. Such restriction of an operating point of the engine is executed not only in the vehicles propelled by the engine but also in hybrid vehicles propelled by the engine and a motor.
When the vehicles operated autonomously e.g., by the control apparatus of JP-A-2014406854 while carrying a passenger, ride comfort may be improved by restricting the operating point of the engine to reduce the noises and vibrations of the engine. However, the engine may not be operated in an optimally fuel efficient manner if the operating point is restricted. That is, if the operating point of the engine is restricted in a steady pattern, an energy efficiency of the engine may be reduced especially when propelling the vehicle autonomously without carrying the passenger.